/*
 * Copyright ConsenSys AG.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
package org.hyperledger.besu.evm.operation;

import org.hyperledger.besu.datatypes.Address;
import org.hyperledger.besu.evm.EVM;
import org.hyperledger.besu.evm.Gas;
import org.hyperledger.besu.evm.account.Account;
import org.hyperledger.besu.evm.frame.ExceptionalHaltReason;
import org.hyperledger.besu.evm.frame.MessageFrame;
import org.hyperledger.besu.evm.gascalculator.GasCalculator;
import org.hyperledger.besu.evm.internal.FixedStack.OverflowException;
import org.hyperledger.besu.evm.internal.FixedStack.UnderflowException;
import org.hyperledger.besu.evm.internal.Words;

import java.util.Optional;

import org.apache.tuweni.units.bigints.UInt256;

public class ExtCodeHashOperation extends AbstractOperation {

  public ExtCodeHashOperation(final GasCalculator gasCalculator) {
    super(0x3F, "EXTCODEHASH", 1, 1, 1, gasCalculator);
  }

  protected Gas cost(final boolean accountIsWarm) {
    return gasCalculator()
        .extCodeHashOperationGasCost()
        .plus(
            accountIsWarm
                ? gasCalculator().getWarmStorageReadCost()
                : gasCalculator().getColdAccountAccessCost());
  }

  @Override
  public OperationResult execute(final MessageFrame frame, final EVM evm) {
    try {
      final Address address = Words.toAddress(frame.popStackItem());
      final boolean accountIsWarm =
          frame.warmUpAddress(address) || gasCalculator().isPrecompile(address);
      final Optional<Gas> optionalCost = Optional.of(cost(accountIsWarm));
      if (frame.getRemainingGas().compareTo(optionalCost.get()) < 0) {
        return new OperationResult(
            optionalCost, Optional.of(ExceptionalHaltReason.INSUFFICIENT_GAS));
      } else {
        final Account account = frame.getWorldUpdater().get(address);
        if (account == null || account.isEmpty()) {
          frame.pushStackItem(UInt256.ZERO);
        } else {
          frame.pushStackItem(UInt256.fromBytes(account.getCodeHash()));
        }
        return new OperationResult(optionalCost, Optional.empty());
      }
    } catch (final UnderflowException ufe) {
      return new OperationResult(
          Optional.of(cost(true)), Optional.of(ExceptionalHaltReason.INSUFFICIENT_STACK_ITEMS));
    } catch (final OverflowException ofe) {
      return new OperationResult(
          Optional.of(cost(true)), Optional.of(ExceptionalHaltReason.TOO_MANY_STACK_ITEMS));
    }
  }
}
